1. Field of the Invention
The present invention relates to an automatic document feed device in an image reading apparatus and, more particularly, to an automatic document feed device having a conveyer path in which documents are discharged one by one, automatically fed to an image reading position, thereafter, reversed, and fed again to the image reading position so as to read out images of two sides of the document.
2. Description of the Related Prior Art
In automatic document feed devices used for image forming apparatuses such as a copying machine, facsimile, and image scanner, at least one document set in a feed tray is automatically fed to an image reading unit and is discharged into the feed tray after completing the image reading operation. In general, adjusting means for correcting a skew of the document is provided in a conveyer path ranging from the feed tray to the image reading unit. More specifically, a pair of rollers is provided in the conveyer path ranging from the feed tray to the image reading unit, and the adjusting means corrects the skew of the document in a conveying direction thereof by nipping a predetermined amount of the edge of the document during the stop state of the pair of rollers.
FIG. 25 shows a conventional automatic document feed device which has been proposed, capable of reading images of double sides of document. In the proposed automatic document feed device, a large-sized conveyer roller 101 carries documents discharged from a feed tray 100 to an document reading unit 102 which is opposed to reading means 111 in an image reading apparatus main body 110. Then, the reading means 111 in the document reading unit 102 reads out a front side of the document. The document is reversed through a switch-back path 103 which is arranged onto the downstream, and the reversed document is carried on a peripheral surface of the conveyer roller 101 again, thereby reading the rear surface of the document. Further, the document of which front and rear sides are read is reversed through the switch-back path 103 and the document reading unit 102, and is discharged on a discharge tray 104 so as to sequentially arrange pages in order upon discharging the documents.
In the automatic document feed apparatus 110, the document reeled from the feed tray 100 is nipped between a pair of rollers 106 by using a feed roller 105 arranged upstream so as to correct the skew of the document. Then, the edge of the document is abutted to a roller 107 pressed against the conveyer roller 101 by using the switch-back roller 108 while carrying the document whose front side is read from the switch-back path 103 to the document reading unit 102, thereby correcting the skew of the document.
An example of the above-mentioned automatic document feed devices is disclosed in Japanese Unexamined Patent Application Publication No. 8-133551. In this disclosure, an document on the feed tray 100 is fed onto a platen and is shifted on the platen. Reading means stopped downstream of the platen reads out an image of the front side of the document. The document after the reading operation on the platen is switched back on a discharge tray and is reversed and supplied again on the platen. The back-side image of the document is read. The discharge tray is arranged downstream of the feed tray and the document is switched back between the feed tray and the discharge tray, thus reducing in size of the automatic document feed device.
However, in the above conventional automatic document feed device, a position of the document fed from the feed tray 100 is provided independently of that to correct the document which is fed to the document reading unit 102 again via the switch-back path 103 after reading the front side of the document by the document reading unit 102. Therefore, a feed path is prolonged and the device has a large size. As a result, the structure becomes complicated.
Also, in the above-mentioned conventional document feed devices, a jammed document in a feed path is removed by opening/closing a part of the feed path, excluding a drive roller, etc., ranging from the feed tray to the platen. The automatic document feed device is opened/closed to the platen and, thereby, the jammed document is removed from a conveyer and discharge path.
However, the device disclosed in the Japanese Patent Application Publication No. 8-133551 has a problem in that the jammed document cannot be easily removed depending on a position of the jammed document because a conveyer path of the document is complicated. In particular, in case of jammed document having a short length in the conveying direction, frequently, only a part of the document is exposed and is sandwiched between a pair of rollers, as components forming the conveyer path, for moving the document. Even if the exposed part can be caught, the document is frequently broken to be forcedly pull out because the document is nipped between the rollers.
Further, it has been extremely difficult to remove the document jammed in a re-feed path which includes a switchback path to change the direction of the document move in order to feed the other surface of the document onto the platen again by turning over the document, because the document is not exposed at all in the re-feed path (referred often as “a switch-back path” thereafter).
As described above, to remove the jammed document in the cycle path for feeding the document again by switching the document to back, a part of the path is opened/closed. However, since feed means such as the feed rollers cannot be arranged to the feed path in the upper direction of the opened/closed cycle, the feed means must be disposed while preventing the upstream of the opened/closed cycle path so as to have the above structure. Consequently, there is a problem in that the device becomes large-sized.